The present invention relates to the cleaning, the disinfection and the sterilization of hemodialysis apparatus.
Such apparatus are frequently used in the hospitals for the treatment of sick persons suffering from acute or chronic renal insufficiency. These sick persons are indeed subjected to a blood purifying system called hemodialysis which consists in maintaining the ionic equilibrium of the blood, eliminating the products resulting from the metabolism, mainly proteins and maintaining the hydric equilibrium of the organism.
This is carried out by means of the hemodialyser which comprises a semi-permeable membrane which separates two circuits, namely the one where the blood of the patient is flowing and the other one where the dialysis liquid is flowing and which contains a solution based upon an electrolytic composition identical with that of the intercellular liquid. The membrane of this hemodialyser allows the passage of substances of a small and medium molecular size up to molecular masses of 10 to 40,000 daltons.
The operation of the hemodialyser is controlled by an apparatus called hemodialysis control device or still more usually artificial kidney or kidney machine. The latter also performs the function of making the dialysis liquid consisting of a solution of sodium, potassium, calcium and magnesium salts and mixed with a substantial amount of glucose. This liquid is heated up to 37.degree. C. and then flows through the hemodialyser where it receives organic substances originating from the blood through the membrane. These organic substances on the one hand and inorganic substances such as calcium and magnesium salts on the other hand would deposit or precipitate onto the inner surfaces of the circuits of the hemodialysis control device.
Moreover, during the manipulations, small leaks may occur and contaminate or infect the machine. This would result in a substantial hazard of contamination or infection of the patient and of the personnel using this equipment.
It is the reasons why, the hemodialysis apparatus is disinfected after each treatment to remove the bacterial contamination which is developing owing to propicious moisture, temperature, time conditions and in the presence of nutritive substances. Furthermore, owing to the presence of germs in the circuits, it is important to disinfect in view of the substantial risk represented by any infection by the micro-organisms.
Therefore, the cleaning, disinfection and sterilization of a hemodialysis apparatus should meet the following requirements: elimination of mechanical type barriers which would prevent the intimate contact between the disinfecting product and the germs and elimination of the chemical type barriers which would decrease the effect of the disinfecting product.
Accordingly, the problem is to find a cleaning, disinfecting and sterilizing product which has a bactericidal, sporicidal and virucidal activity, which disperses or scatters the organic deposits built up onto the inner surfaces of the circuit, which dissolves the deposits made of inorganic precipitates, which disinfects very effectively the surfaces in a gaseous phase without wetting them, and finally which is compatible with the materials forming the hemodialysis apparatus.
Now conventionally the hemodialysis apparatus are cleaned and disinfected with sodic hypochlorite (salt of the hypochlorous acid) at 5.25% diluted in tap water at a ratio of 1:35. However, sodic hypochlorite is not stable since even within a pH range of 11-12, its active chlore content rapidly decreases. Besides, sodic hypochlorite is generally obtained by electrolysis with means of electrodes one of which is made of mercury, traces of which are found in the sodic hypochlorite solutions used.
Moreover, such a process is carried out under alkaline conditions with a pH between 11 and 12 or above. Therefore, a great number of lipidic or proteinic compounds (most often polypeptides of low molecular weights) such as urea, creatinine, alkaline hydroxides left as a residue of a previous hemodialysis, would precipitate or settle down. Indeed, these compounds as well as the bacteria and the viruses have passed through the semi-permeable membrane of the dialyser from the blood of the sick person to the hemodialysis device. This cleaning operation would be repeated. Consequently, the incrustation of deposits would increase with the number of treatments, and an environment suitable to the microorganisms such as the locations and the porosities of the surfaces in the apparatus, promotes said incrustation of deposits. Cross infections could even be generated in such a case.
After two weeks of continuous use of the dialysis apparatus at a rate of three daily dialysis performances or courses lasting each one 3 or 4 hours with a cleaning-disinfection step between each performance or course (when changing from one patient to another one), the encrusting is such that it is necessary to undertake a more effective cleaning. At this stage, acid solutions are used for removing the encrusted deposits, in other words for descaling the apparatus. Generally, these solutions are based upon oxalic acid or a mixture of oxalic acid and acetic acid. This oxalic acid is used in view of its incrustations-dissolving properties and of its anti-chlorine and anti-rust properties as well as of its absence of corrosive activity on stainless steel, nylon, silicone gum, teflon and glass which are the usual components of these apparatus. When however this de-encrusting phase is completed, any trace of acid should be removed. Oxalic acid being toxic indeed is dangerous for the next patient which undergoes the dialysis.
A washing is then carried out with a solution of bicarbonate which is neutralizing.
However, in spite of the de-encrusting step followed by the neutralizing washing, it is difficult to remove all the traces of virus and bacterium which may remain in the most inaccessible portions of the hemodialysis apparatus such as the gauges or the joints of the various valves.
With such conditions, a last treatment is required: a sterilization with formol, i.e. formaldehyde, every month or every month and one half.
This treatment is carried out in a vapor phase where it is possible to reach invisible places or those places where the liquid does not act because of the air. Generally, the operators are using formol to eliminate a contamination by Pseudomonas aeruginosa.
This cleaning process requires to stop the apparatus for at least 24 hours. Moreover, traces of formol may remain in the apparatus and this is not without danger in view of the mutagen character of formol. Besides, the use of formol is awkward since it is an irritating and toxic agent.
The object of the present invention accordingly is a method of cleaning, disinfecting and sterilizing hemodialysis apparatus in a single step, which would allow to eliminate both the organic deposits and the inorganic precipitates while providing a bactericidal, sporicidal and virucidal activity and a disinfecting activity in a gaseous phase.
The method according to the invention consists in:
mixing a basic composition comprising the chlorite ion with an acid composition comprising lactic acid in a mass ratio of the basic composition to the acid composition ranging from 1:6 to 1:3,
feeding the mixture thus obtained and added with water into a hemodialysis apparatus, the volume ratio of the mixture to water being of about 1:34, and
circulating the final solution in the apparatus wherein the mixture is diluted in water and the basic composition is reacted with the acid composition.
According to an advantageous feature of the invention, the mass ratio of one basic composition to the acid composition is preferably of about 1:5.
The invention will be better understood and further objects, characterizing features, details and advantages thereof will appear more clearly as the following explanatory description proceeds with reference to the accompanying diagrammatic drawing given by way of non limiting example only illustrating on the single Figure thereof as presently preferred specific embodiment of the invention.